1. Field of the Invention
The present invention relates generally to surge detection devices, and, more particularly, to methods and apparatuses for detecting surge in a compressor of a compressor-driven system, such as a refrigeration system.
2. Description of the Related Art
As is generally known, surge or surging is an unstable condition that may occur when compressors, such as centrifugal compressors, are operated at light loads and high pressure ratios. It is a transient phenomenon characterized by high frequency oscillations in pressures and flow, and, in some cases, the occurrences of a complete flow reversal through the compressor. Such surging, if uncontrolled, causes excessive vibrations in both the rotating and stationary components of the compressor, and may result in permanent compressor damage. In particular, at surge conditions there exists a momentary reduction in flow and pressure developed across the compressor. Further, there is a reduction in the net torque and mechanical power at the compressor driving shaft. In the case where the drive device is an electric motor, these oscillations in torque and power will cause oscillations in motor current and excessive electrical power consumption.
While a number of surge detection devices and systems have been utilized, there exists a need for an improved surge detection arrangement, particularly but not exclusively, for use in refrigeration systems having a centrifugal compressor driven by an electric motor.